1. Field of the Invention
The present invention relates to improvements in vacuum cleaners having a rotary brush in the dust intake opening portion.
2. Prior Art
With vacuum cleaners having a rotary brush in the dust intake opening portion, it is likely that a carpet or the like will be caught by the rotary brush to stall the brush during cleaning. If the motor for driving the brush continues to rotate in this state, the motor pulley rubs against the stopped belt, producing heat of friction to break the belt. Furthermore, the drive motor, which is also overloaded, will burn out.
To eliminate the above drawback, Unexamined Japanese Patent Publication No. SHO 58-86121 discloses a cleaner wherein when the rotary brush becomes stalled, a clutch provided between the brush and the drive motor therefor operates to turn off a switch and stop the motor, whereby the belt is prevented from breaking. However, the cleaner is inefficient and very costly to fabricate and has a likelihood of malfunction because of its complex structure including the clutch and two belts.
U.S. Pat. No. 3,757,382 discloses an arrangement which is adapted to reduce the friction between the rotary brush pulley and the belt when the rotary brush becomes stalled. Nevertheless, the arrangement is complex in construction and requires a cumbersome and costly procedure for fabrication because the pulley comprises a plurality of rollers.
Unexamined Japanese Patent Publication No. SHO 59-192321 discloses an arrangement wherein the drive motor for the rotary brush is supported by an elastic body to tilt the motor and thereby shift the belt when the brush is stalled, such that the shift of the belt is detected to stop the motor. However, it is extremely difficult to adjust the degree of elasticity with which the motor is supported tiltably, because if supported too rigidly, the motor will not tilt, whereas if supported too elastically, the motor will be unstable at all times.